Hydrus is a medium eel like colossi found at Relic Lake. Fur and moss cover most of his body and three orange rods line his back. The rods produce electricity when underwater and stabbing a weak spot/injury at the base of each will cause them to turn black and no longer work. The end of his tail is paddle like and raises out of the water like a whales. He is the seventh colossi encountered and a sigil is located on his head.